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  • richardmitnick 1:20 pm on June 10, 2013 Permalink | Reply
    Tags: , DZero, , , ,   

    From Fermilab: “DZero collaboration meeting reviews Tevatron legacy” 

    Fermilab is an enduring source of strength for the US contribution to scientific research world wide.

    DZer0

    No one should ever forget the value of the work of the Tevatron. The work of the Tevatron led directly to the success of the LHC.

    Monday, June 10, 2013
    No Writer Credit

    “This week the DZero collaboration is holding a workshop on the plains of DeKalb, Ill., as it plans its final campaign to review the legacy of the Tevatron. This is the 30th year that DZero has held its regular week-long workshops. With the unique Tevatron proton-antiproton data set, fully developed particle identification and well-established computing in hand, the experiment analysis teams are in position to address the most important topics of particle physics. At the workshop, scientists are discussing plans for the publication of more than 50 legacy results from the full Tevatron data set, including precision measurements of such fundamental Standard Model parameters as masses of the top quark and W boson and result combinations with the CDF and LHC experiments. Learn more about this week’s workshop.

    Large particle collider experiments tackle a panoply of distinct physics questions, each of which requires inputs from many algorithm and calibration tools. Weaving these disparate threads into a coherent tapestry requires a huge effort. The DZero collaboration has used these week-long collaboration-wide workshops to step back and view the overall effort and provide comprehensive guidance.

    Fermilab campus

    Fermilab Tevatron
    Tevatron

    Fermi National Accelerator Laboratory (Fermilab), located just outside Batavia, Illinois, near Chicago, is a US Department of Energy national laboratory specializing in high-energy particle physics.


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  • richardmitnick 12:22 pm on April 18, 2013 Permalink | Reply
    Tags: , DZero, , , , , ,   

    From Fermilab- “Frontier Science Result: DZero Precise measure of matter preference 

    Fermilab is an enduring source of strength for the US contribution to scientific research world wide.

    Thursday, April 18, 2013
    Mike Cooke

    “We live in a universe filled with matter, with no detectable pockets of antimatter, but don’t fully understand why. In the very early universe, matter and antimatter were created in equal abundance. As the universe cooled, the matter and antimatter annihilated each other, but left behind the small excess of matter that accounts for all of the stars, planets and galaxies in the universe today. This difference is thought to result from the slightly different ways the particles and antiparticles decayed. However, the decay rate difference predicted by the Standard Model is not nearly enough to account for the amount of matter in the universe. By precisely measuring processes that show a difference between matter and antimatter, physicists attempt to understand what caused the imbalance that led to the universe today.

    scene
    Most matter and antimatter annihilated each other in the very early universe, but a small excess of matter remained to form the universe we live in today. To attempt to understand this imbalance, scientists measure particle decay processes that show a difference between matter and antimatter.

    A recent result at DZero studied this asymmetry in the decay of a charged B meson, made of a bottom quark and an up quark, into a J/Ψ meson and a charged K meson, which involves the bottom quark decaying into a strange quark and two charm quarks. To reduce the uncertainty on the measurement, the analysis exploited the fact that the magnetic polarities of magnets in the DZero detector were systematically flipped during the decade of data collecting for Run II. Each possible source of bias in the measurement of asymmetry between matter and antimatter was carefully studied and accounted for.

    The final result is the world’s most precise measurement of matter-antimatter asymmetry in charged B meson decays to a J/Ψ meson and a charged K meson. The measured asymmetry is consistent with the Standard Model. While it does not indicate the presence of new physics and explain the matter-antimatter asymmetry in the universe, it is an important step in exploring this mystery.”

    See the full article here.

    The final result is the world’s most precise measurement of matter-antimatter asymmetry in charged B meson decays to a J/Ψ meson and a charged K meson. The measured asymmetry is consistent with the Standard Model. While it does not indicate the presence of new physics and explain the matter-antimatter asymmetry in the universe, it is an important step in exploring this mystery.

    Fermilab campus

    Fermi National Accelerator Laboratory (Fermilab), located just outside Batavia, Illinois, near Chicago, is a US Department of Energy national laboratory specializing in high-energy particle physics.


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  • richardmitnick 11:47 am on March 21, 2013 Permalink | Reply
    Tags: , , DZero, , , ,   

    From Fermilab- “Frontier Science Result: CDF CDF finalizes its combined Higgs boson results 

    Fermilab is an enduring source of strength for the US contribution to scientific research world wide.

    Thursday, March 21, 2013
    Andy Beretvas

    “CDF’s physicists have been searching for the Higgs boson since the early days of Run I, publishing their first paper on the search in 1990. If you asked any of them why they did it, they would say it was to learn about what breaks the symmetries of the Standard Model, which is so successful in explaining the data observed at Fermilab and at other particle physics laboratories. Particles cannot have masses if these symmetries hold true, and the Higgs mechanism is the simplest, but not the only, way to resolve this dilemma. On July 4 of last year, two independent experiments at CERN, ATLAS and CMS, announced the observation of a Higgs-like boson. On July 27 Fermilab’s CDF and DZero experiments submitted a combined analysis showing evidence for a Higgs-like particle. The experiments at CERN were primarily finding the decay of the Higgs-like particle into bosons, while the experiments at Fermilab were finding the decay into fermions.

    CDF sought the Higgs boson in many production and decay modes over the years. These searches have now been finalized and documented. The combined results of all of these analyses have been put together and are the last pieces of the chain. Each analysis relied upon the excellent performance of the Tevatron collider and the CDF detector.

    The collaborations will soon submit a new paper that finalizes the combined CDF and DZero result.

    See the full article here.

    graph
    Best-fit cross section for inclusive Higgs boson production, normalized to the Standard Model expectation, for the combination of all CDF search channels as a function of the Higgs boson mass. The solid line indicates the fitted cross section, and the associated shaded regions show the 68 percent and 95 percent credibility intervals, which include both statistical and systematic uncertainties.

    s,
    Standard Model with Higgs

    collab
    The CDF collaboration celebrates the Tevatron on Sept. 30, 2011. Photo: Cindy Arnold

    Fermilab campus

    Fermi National Accelerator Laboratory (Fermilab), located just outside Batavia, Illinois, near Chicago, is a US Department of Energy national laboratory specializing in high-energy particle physics.


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  • richardmitnick 10:26 am on February 14, 2013 Permalink | Reply
    Tags: , , DZero, , , , ,   

    From Fermilab- “Frontier Science Result: DZero Deciphering the Higgs signature” 

    Fermilab is an enduring source of strength for the US contribution to scientific research world wide.

    Thursday, Feb. 14, 2013
    Mike Cooke

    The search for the Higgs boson begins by looking for its signature, or the final decay products that are measured by the detector…
    higgs
    A “Higgs event” from CMS at CERN.

    … Because it has many ways of being produced and decaying, Higgs boson events have numerous signatures, and a particular signature may be shared by multiple production and decay modes. After a signature is identified, it must be deciphered while considering all possible sources of signal and background. A recent result from DZero focuses on the study of one specific signature, consisting of an electron or muon, missing energy indicating a neutrino, and two or more jets of particles.

    No significant excess of events was observed when considering this Higgs signature on its own, but its sensitivity will be an important contribution to the combined Higgs boson results from DZero and the Tevatron.”

    See the full article here, and understand that while the Tevatron is no longer operating in the hunt for Higgs, its story is not yet finished. There is still a great deal of data to be analyzed.

    Fermilab campus

    Fermilab Tevatron
    Tevatron at Frmilab

    Fermi National Accelerator Laboratory (Fermilab), located just outside Batavia, Illinois, near Chicago, is a US Department of Energy national laboratory specializing in high-energy particle physics.


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  • richardmitnick 12:20 pm on January 17, 2013 Permalink | Reply
    Tags: , DZero, , , , ,   

    From Fermilab: “Frontier Science Result: DZero Right size, wrong shape for Z’s with b’s” 


    Fermilab is an enduring source of strength for the US contribution to scientific research world wide.

    Thursday, Jan. 17, 2013
    Mike Cooke

    “To estimate a signal or background process at a particle collider, two seemingly simple questions must be answered: ‘How much of it is there?’ and ‘Where will it appear in the detector?’ Knowing the rate and shape of each process is necessary to build an analysis that can reject backgrounds while keeping and measuring the signal. But interactions that involve the strong force are particularly difficult to predict directly from the theory and instead are estimated from models that are constrained by experimental data. Some of these processes, especially those involving weak force bosons and b’s, or bottom quarks, are important backgrounds to precision studies of the top quark and the Higgs boson. A recent analysis at DZero focuses on testing whether models are correctly estimating the rate and shape of events with a Z boson and a bottom quark….”

    Now it is getting deep, so visit the full article here.

    dz
    DZero

    Fermilab campus

    Fermi National Accelerator Laboratory (Fermilab), located just outside Batavia, Illinois, near Chicago, is a US Department of Energy national laboratory specializing in high-energy particle physics.


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  • richardmitnick 11:57 am on January 3, 2013 Permalink | Reply
    Tags: , DZero, , , ,   

    From Fermilab: “Frontier Science Result: DZero – The bosons and the b’s” 


    Fermilab is an enduring source of strength for the US contribution to scientific research world wide.

    Thursday, Jan. 3, 2013
    Mike Cooke

    Studies of the newly observed Higgs-like boson, measurements of the top quark and many searches for exotic physics cannot happen without first understanding the fundamental interactions that introduce certain naturally occurring background processes in the Standard Model: the bosons and the b’s.

    The basic interactions that can create a W boson along with one or more bottom quarks are difficult to model, even though the process occurs with great frequency at hadron colliders.

    A recent result from DZero examines this particular production process, providing important input for further model development and a crucial cross-check of existing experimental results.

    DZero
    DZero

    The DZero analyzers measure a production rate that is consistent with that predicted by a number of existing theoretical models.

    See the full and deep article here.

    Fermi National Accelerator Laboratory (Fermilab), located just outside Batavia, Illinois, near Chicago, is a US Department of Energy national laboratory specializing in high-energy particle physics.


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  • richardmitnick 12:24 pm on April 6, 2012 Permalink | Reply
    Tags: , DZero, , , , ,   

    From Fermilab Today: “Subatomic CSI” – A Great Detailed Explication of Evidence for Higgs 

    Fermilab continues to be a great source of strength in the U.S. Basic Research Community.

    Don Lincoln
    Friday, April 6, 2012

    “If we find the Higgs boson, we won’t see the particle itself. Instead, we will see its decay products interacting with the detector. To find out if the original particle is the Higgs, we do particle physics forensics.

    If Higgs theory is correct and it exists in the suspected mass range, the Higgs boson has a lifetime of about 10^-22 seconds. Even if it is moving at the speed of light, the Higgs boson will travel a distance only a few times the size of a proton before it decays. That’s too quick for us to observe, so we have to look at the end result. For simplicity, let’s say the Higgs boson decays into two Z bosons, even though that’s rare in that mass range.

    If one Z boson decays into an electron-positron pair, while the other Z boson decays into a matter-antimatter pair of muons, we can see the relatively stable electrons and muons in the detector.

    If we only see the electrons and muons, how do we know what started the decay chain? Referred to as the parent, the original particle decays into daughter particles, their decay products are granddaughter particles and so on. To determine the original ancestor, we exploit basic energy and momentum conservation laws. The generations have exactly the same energy and momentum, since energy and momentum are conserved. For instance, if we take the two muon granddaughter particles and precisely measure their energy and momentum, we can combine them and determine the energy and momentum of their parent, one of the Z particles. Do the same for the other Z particle, and we can combine the energy and momentum of the two daughter Z bosons to determine the energy and momentum of the parent particle that might be a Higgs boson.”

    i1
    The detector at Fermilab, now gone to its resting place

    This is the full article. There is a link to a further explanation on “how decay products lead to the original product.” See everything here.

     
  • richardmitnick 2:43 pm on March 2, 2012 Permalink | Reply
    Tags: , , DZero, , , , , , ,   

    From Fermilab: “World’s best measurement of W boson mass points to Higgs mass and tests Standard Model” 

    Fermilab continues to be a great source of strength in the U.S. Basic Research Community.

    Tona Kunz
    March 2, 2012

    “The world’s most precise measurement of the mass of the W boson, one of nature’s elementary particles, has been achieved by scientists from the CDF and DZero collaborations at the Department of Energy’s Fermi National Accelerator Laboratory. The new measurement is an important, independent constraint of the mass of the theorized Higgs boson. It also provides a rigorous test of the Standard Model that serves as the blueprint for our world, detailing the properties of the building blocks of matter and how they interact.

    The Higgs boson is the last undiscovered component of the Standard Model and theorized to give all other particles their masses. Scientists employ two techniques to find the hiding place of the Higgs particle: the direct production of Higgs particles and precision measurements of other particles and forces that could be influenced by the existence of a Higgs particles. The new measurement of the W boson mass falls into the precision category.

    See the full very exciting article here.

     
  • richardmitnick 8:56 pm on December 20, 2011 Permalink | Reply
    Tags: , DZero, , , ,   

    From Fermilab Today: “Illuminating the Z boson” 

    Fermilab is an enduring source of strength for the US contribution to scientific research world wide.

    i1
    DZero physicists looked for evidence of the Z boson directly emitting light, a process that is not part of the Standard Model.


    Standard Model

    Mike Cook
    Dec 20 2011
    “According to the Standard Model, the Z boson lives its life in the dark. Lacking an electric charge, this weak force carrier is ignored by photons. Their only interactions are indirect, with their communication mediated by charged particles. They can only be produced at the same time if light is emitted by a charged particle that either helped make or was made by the Z boson.

    But what if a Z boson could emit light, or a photon could emit a Z boson? While not part of the Standard Model, these interactions can be modeled and tested for by carefully studying events where both a Z boson and a high-energy photon are produced at the same time. This precision test of the Standard Model allows us to search for new physics in a generalized way, without needing to have a specific new theory in mind to perform the analysis.

    Physicists at DZero have recently completed just such a detailed analysis of events with a photon and a Z boson.”

    Read the full article for the rest of the story.

     
  • richardmitnick 4:08 pm on December 15, 2011 Permalink | Reply
    Tags: , , DZero, , ,   

    From Fermilab Today: “A new way to find the top” 

    Fermilab is an enduring source of strength for the US contribution to scientific research world wide.

    Edited by Andy Beretvas
    Dec. 15, 2011

    “As we learned on Dec. 13, finding the Higgs boson is proving to be more of a challenge every day. CDF scientists are using the top quark to try to pin down the preferred mass of the Higgs indirectly. In the Standard Model, the mass of the top quark, W boson and Higgs boson are all inter-related. If you know any two of the three exactly, you can predict the mass of the third. That’s one of the motivations for scientists to measure the top quark mass with high precision—to get further insight into the mass of the long-hypothesized, but still undetected, Higgs boson.

    i1
    A collision event involving top quarks

    Since the discovery of the top quark at the Tevatron by CDF and DZero in 1995, scientists have made dozens of top quark mass measurements using various decay modes of the top and anti-top quark pair. Recently, CDF physicists made a measurement of the top quark mass with an entirely new set of data. This measurement will add unique information into the overall picture of the top quark mass and improve the precision of its mass measurement.”

    See the full article here.


     
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